Scott Fitzgerald, Gatsby's past is revealed very gradually throughout the story. It is revealed shortly in a couple parts in the story, and then it is blown open in Chapter 6. This technique is used so that Gatsby can remain a "mystery" throughout the book. Also, it is used to keep Gatsby's image of being rich and famous, throughout the story.
We first learn about Gatsby in the first chapter. We briefly get a description of Gatsby. We learn that he lives in the same place as Nick. They both live in West Egg, which is the place for the "new rich". That is simply a term that means the people that live there have acquired their money recently, or it was not inherited. We also learn that Gatsby stands outside his house, looking across the bay at a single green light. This technique of learning of Gatsby is a really good one. Nick never really sees Gatsby, he only sees his shadow. That shows that Gatsby is already a man of mystery. We do not really get a good look at him, just an outline of his figure. We do not know what is the deal with him and the green light. The technique is used so that we can only catch a glimpse of him, and make us want to read on to find out what he really looks like and what is the big mystery about him.
Now, the name of the book is called "The Great Gatsby", but we have never seen him, except the shadow in chapter 1, nor have we have any idea of why he is "great". We first see him through the eyes of others. Catherine Wilson told Nick in chapter 2, that she heard that Gatsby was a nephew or cousin of Kaiser Wilhelm. Lucille, a friend of Jordan, thinks that Gatsby was a German spy during the war. The world is full or rumors of him, but we have no idea if any of them are true. That is why Fitzgerald wrote the book this way. It is a mystery for us to solve. In chapter 3, we get to see what his house is like, and what his parties are about. He has a Rolls, a station wagon, 2 boats, aquaplanes, a swimming pool, and a real beach.